20,200 research outputs found
Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with WMAP and the COSMOSOMAS Experiment
We present evidence for anomalous microwave emission (AME) in the Pleiades
reflection nebula, using data from the seven-year release of the Wilkinson
Microwave Anisotropy Probe (WMAP) and from the COSMOSOMAS experiment. The flux
integrated in a 1-degree radius around R.A.=56.24^{\circ}, Dec.=23.78^{\circ}
(J2000) is 2.15 +/- 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data
show no significant emission, but allow to set upper limits of 0.94 and 1.58 Jy
(99.7% C.L.) respectively at 10.9 and 14.7 GHz, which are crucial to pin down
the AME spectrum at these frequencies, and to discard any other emission
mechanisms which could have an important contribution to the signal detected at
22.8 GHz. We estimate the expected level of free-free emission from an
extinction-corrected H-alpha template, while the thermal dust emission is
characterized from infrared DIRBE data and extrapolated to microwave
frequencies. When we deduct the contribution from these two components at 22.8
GHz the residual flux, associated with AME, is 2.12 +/- 0.12 Jy (17.7-sigma).
The spectral energy distribution from 10 to 60 GHz can be accurately fitted
with a model of electric dipole emission from small spinning dust grains
distributed in two separated phases of molecular and atomic gas, respectively.
The dust emissivity, calculated by correlating the 22.8 GHz data with
100-micron data, is found to be 4.36+/-0.17 muK/MJy/sr, a value that is rather
low compared with typical values in dust clouds. The physical properties of the
Pleiades nebula indicate that this is indeed a much less opaque object than
others were AME has usually been detected. This fact, together with the broad
knowledge of the stellar content of this region, provides an excellent testbed
for AME characterization in physical conditions different from those generally
explored up to now.Comment: Accepted for publication in ApJ. 12 pages, 8 figure
Active materials for adaptive architectural envelopes based on plant adaptation principles
In this paper, the authors present research into adaptive architectural envelopes that adapt to environmental changes using active materials, as a result of application of biomimetic principles from plants to architecture. Buildings use large amounts of energy in order to maintain their internal comfort, because conventional buildings are designed to provide a static design solution. Most of the current solutions for facades are not designed for optimum adaptation to contextual issues and needs, while biological solutions to adaptation are often complex, multi-functional and highly responsive. We focus on plant adaptations to the environment, as, due to their immobility, they have developed special means of protection against weather changing conditions. Furthermore, recent developments in new technologies are allowing the possibility to transfer these plant adaptation strategies to technical implementation. These technologies include: multi-material 3D printing, advances in materials science and new capabilities in simulation software. Unlike traditional mechanical activation used for dynamic systems in kinetic facades, adaptive architectural envelopes require no complex electronics, sensors, or actuators. The paper proposes a research of the relationship that can be developed between active materials and environmental issues in order to propose innovative and low-tech design strategies to achieve living envelopes according to plant adaptation principles
Use of UV-vis Reflection Spectroscopy for Determining the Organization of Viologen and Viologen Tetracyanoquinodimethanide Monolayers.
Use of UV-vis Reflection Spectroscopy for Determining the Organization of Viologen and Viologen Tetracyanoquinodimethanide Monolayers.
Generalized messengers of supersymmetry breaking and the sparticle mass spectrum
We investigate the sparticle spectrum in models of gauge-mediated
supersymmetry breaking. In these models, supersymmetry is spontaneously broken
at an energy scale only a few orders of magnitude above the electroweak scale.
The breakdown of supersymmetry is communicated to the standard model particles
and their superpartners by "messenger" fields through their ordinary gauge
interactions. We study the effects of a messenger sector in which the
supersymmetry-violating F-term contributions to messenger scalar masses are
comparable to the supersymmetry-preserving ones. We also argue that it is not
particularly natural to restrict attention to models in which the messenger
fields lie in complete SU(5) GUT multiplets, and we identify a much larger
class of viable models. Remarkably, however, we find that the superpartner mass
parameters in these models are still subject to many significant contraints.Comment: 24 pages, LaTeX, uses epsf.sty, 4 figures. Assumptions clarified,
numerical bounds tweaked, typos correcte
Accretion-Induced Lithium Line Enhancements in Classical T Tauri Stars: RW Aur
It is widely accepted that much of the stochastic variability of T Tauri
stars is due to accretion by a circumstellar disk. The emission line spectrum
as well as the excess continuum emission are common probes of this process. In
this communication, we present additional probes of the circumstellar
environment in the form of resonance lines of low ionization potential
elements. Using a set of 14 high resolution echelle observations of the
classical T Tauri star (CTTS), RW Aur, taken between 1986 and 1996, we
carefully measure the continuum veiling at each epoch by comparing more than
500 absorption lines with those of an appropriate template. This allows us to
accurately subtract out the continuum emission and to recover the underlying
photospheric spectrum. In doing so, we find that selected photospheric lines
are enhanced by the accretion process, namely the resonance lines of LiI and
KI. A resonance line of TiI and a low excitation potential line of CaI also
show weak enhancements. Simple slab models and computed line bisectors lead us
to propose that these line enhancements are markers of cool gas at the
beginning of the accretion flow which provides an additional source of line
opacity. These results suggest that published values of surface lithium
abundances of classical T Tauri stars are likely to be overestimated. This
would account for the various reports of surface lithium abundances in excess
of meteoritic values among the extreme CTTS. Computing LTE lithium abundances
of RW Aur in a low and then high accretion state yields abundances which vary
by one order of magnitude. The low accretion state lithium abundance is
consistent with theoretical predictions for a star of this age and mass while
the high accretion state spectrum yields a super-meteoritic lithium abundance.Comment: 28 pages, 8 figures, accepted by Ap
String and string-inspired phenomenology
In these lectures I review the progress made over the last few years in the
subject of string and string-inspired phenomenology. I take a practical
approach, thereby concentrating more on explicit examples rather than on formal
developments. Topics covered include: introduction to string theory, the
free-fermionic formulation and its general features, generic conformal field
theory properties, GUT and string model-building,
supersymmetry breaking, the bottom-up approach to string-inspired models,
radiative electroweak symmetry breaking, the determination of the allowed
parameter space of supergravity models and the experimental constraints on this
class of models, and prospects for direct and indirect tests of string-inspired
models. (Lectures delivered at the XXII ITEP International Winter School of
Physics, Moscow, Russia, February 22 -- March 2, 1994)Comment: CTP-TAMU-17/94, 39 pages (latex), 27 figures (not included). Figures
are available via anonymous ftp from hplaa02.cern.ch (/pub/lopez) as one
uuencoded file (MoscowFigs.uu, 1.31MB
AI-driven web API testing
Testing of web APIs is nowadays more critical than ever before,
as they are the current standard for software integration. A bug
in an organization’s web API could have a huge impact both in ternally (services relying on that API) and externally (third-party
applications and end users). Most existing tools and testing ap proaches require writing tests or instrumenting the system under
test (SUT). The main aim of this dissertation is to take web API
testing to an unprecedented level of automation and thoroughness.
To this end, we plan to apply artificial intelligence (AI) techniques
for the autonomous detection of software failures. Specifically, the
idea is to develop intelligent programs (we call them “bots”) ca pable of generating hundreds, thousands or even millions of test
inputs and to evaluate whether the test outputs are correct based
on: 1) patterns learned from previous executions of the SUT; and 2)
knowledge gained from analyzing thousands of similar programs.
Evaluation results of our initial prototype are promising, with bugs
being automatically detected in some real-world APIs.Ministerio de Economía y Competitividad BELI (TIN2015-70560-R)Ministerio de Ciencia, Innovación y Universidades RTI2018-101204-B-C21 (HORATIO)Ministerio de Educación, Cultura y Deporte FPU17/0407
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